In radiotherapy, the goal is typically to deliver a sufficiently high radiation dose to a target (for example a tumor) within the patient, while sparing surrounding normal tissue as far as possible. In particular, it is important to minimize the dose to sensitive organs close to the target. A treatment plan, defining treatment parameters, such as treatment machine settings, to be used in a radiotherapy treatment session, is usually determined with the aid of a computer-based treatment planning system. In inverse treatment planning, an optimization algorithm is employed for finding a set of treatment parameters that will generate an acceptable dose distribution within the subject, preferably satisfying all the clinical goals defined by the clinician. However, the treatment plan optimization process does not in any way guarantee that the best possible treatment plan is obtained. The result is in general depending on the experience of the treatment planner and, for example, the selection of treatment objectives used for the optimization. A substantial amount of “trial-and-error” is usually required, even for an experienced treatment planner, before an acceptable treatment plan has been found.
Furthermore, if a dose distribution of an optimized treatment plan is satisfactory in most regards but comprises some small deficiency, it might not be apparent to a treatment planner how to adjust the optimization objectives or constraints (or the objective weights) in order to remedy the deficiency.
An aim of the present invention is to overcome, or at least mitigate, the drawbacks described above, and in particular to provide a treatment planning system that will enable a treatment plan to be generated that satisfies clinical goals to a greater extent.